The present invention resides in the field of assays to determine the capacity of blood platelets to aggregate.
Although the causes of abnormal blood clotting are many, one cause which has been of particular importance is an abnormal platelet condition which renders the platelets unable to aggregate, a phenomenon essential to normal clotting. This abnormal platelet condition can be either a deficiency in the number of platelets in the patient's blood, or a defect in the platelets.
As an example, it has been discovered that full-term pregnancy pre-eclamptic women often have prolonged bleeding times. This has been attributed to low platelet counts, and also in some instances is thought to be due to abnormalities in platelets. See, J. Ramanathan et al., Anesthesiol., 1989, 71, 188-91. Additionally, in the area of quality control, a recent article points up the need for a sensitive test which can be used to differentiate platelet concentrates which retain functional integrity after storage from those which do not, and explains that there is presently no available method for accomplishing this. T. Hervig et al., Clin. Chem., 1990, 36, No. 1, pp. 28 -31.
Prior known and used tests for screening for abnormal platelet conditions are expensive and complicated. For example, the test currently used clinically is known as a platelet aggregation test. Generally, this test is performed by using expensive reagents such as ristocetin, collagen, adenosine diphosphate, or other reagents. Since these reagents work poorly, a sensitive optical instrument is used to follow the reaction. These tests, because of their inherent insensitivity, yield little clinically useful results. Needless to say, this test is not only costly, but also time consuming. Moreover, it cannot be conducted in the physician's office, necessitating sending samples to specialized laboratories for testing.
What is therefore needed is an initial screen test for determining the capacity of a patient's platelets to aggregate which is simple, inexpensive, and which can be conducted rapidly in a physician's office. Depending on the outcome of this initial screen, further, more quantitative testing for platelet aggregation may or may not be indicated. The present invention addresses this need.